Selective catalytic oxidation of DMF over Cu-Ce/H-MOR by modulating the surface active sites

Selective catalytic oxidation of the hazardous DMF exhaust gas presents a significant challenge in balancing oxidation activity and products selectivity (CO, NO_x, N₂, etc.). It is found that Cu/H-MOR demonstrates superior performance for DMF oxidation compared to CuO on other supports (γ-Al₂O₃, HY, ZSM-5) in terms of product selectivity and stability. The geometric and electronic structures of CuO active sites in Cu/H-MOR have been regulated by CeO₂ promoter, leading to an increase in the ratio of active CuO (highly dispersed CuO and Cu⁺ specie). As a result, the oxidation activity and stability of the Cu/H-MOR catalyst were enhanced for DMF selective catalytic oxidation. However, excessive CuO or CeO₂ content led to decreased N₂ selectivity due to over-high oxidation activity. It is also revealed that Ce³⁺ species, active CuO species, and surface acid sites play a critical role in internal selective catalytic reduction reaction during DMF oxidation. The 10Cu-Ce/H-MOR (1/4) catalyst exhibited both high oxidation activity and internal selective catalytic reduction activity due to its abundance of active CuO specie as well as Ce³⁺ species and surface acid sites. Consequently, the 10Cu-Ce/H-MOR (1/4) catalyst demonstrated the widest temperature window for DMF oxidation with high N₂ selectivity. These findings emphasize the importance of surface active sites modification for DMF selective catalytic oxidation.